Electrolysis cell, in particular for use in a plant for producing an electrochemically activated sodium chloride solution, and plant having a number of such electrolysis cells

ABSTRACT

An electrolysis cell, in particular for producing an electrochemically activated sodium chloride solution, includes an anode chamber provided with an anode and a cathode chamber separated therefrom by a membrane and provided with a cathode. The membrane is designed as a hollow ceramic cylinder surrounded by an outer housing and is intended to make it possible to produce a particularly high-quality, electrochemically activated sodium chloride solution. The ends of the hollow ceramic cylinder and the outer housing surrounding the cylinder are each mounted in a closure cap, which has a central hole forming an entry channel to the interior of the hollow ceramic cylinder and an annular chamber that extends around the central hole and, on the media side, is connected to the intermediate chamber between the membrane and the outer housing.

The invention relates to an electrolysis cell, in particular for producing an electrochemically activated sodium chloride solution, comprising an anode chamber provided with an anode and a cathode chamber separated therefrom by a membrane and provided with a cathode, the membrane being designed as a hollow ceramic cylinder surrounded by an outer housing. The invention also relates to a plant for producing an electrochemically activated solution, having an electrolysis module which comprises a plurality of electrolysis cells of this type.

Many documents, for example DE 30 003 131 A1, U.S. Pat. No. 4,056,452, EP 1 728 768 A1 or European patent application 10 003 555.9-2104, disclose electrolysis devices or plants for producing an electrochemically activated solution by electrolysing briny water, in which one or more electrolysis cells are used which comprise an anode chamber and a cathode chamber which are separated from each other by a membrane. In plants of this type, a flow of water supplied with a sodium chloride solution or with brine is fed to the electrolysis device and is electrolytically decomposed at said device to produce the electrochemically activated sodium chloride solution by electrolysis. An electrochemically activated aqueous saline solution is obtained thereby which has a comparatively high content of free chlorine and a comparatively high redox potential. The electrochemically activated saline solution which can be obtained thereby is particularly suitable for use as a disinfectant, for example for disinfecting water and/or aqueous solutions.

When producing the electrochemically activated saline solution in the above-mentioned manner, particularly high activity or biocidity of the produced substance, usually characterised by a particularly high content of free chlorine and/or a sufficiently high redox potential, is usually sought. In addition, in particular in view of possible applications of such substances as disinfectants or also as an additive, carrier substance or even an active substance in medical or therapeutic preparations, it is desirable for the high activity, especially in view of particularly good storage stability, to remain largely unchanged or to have only slight changes even after comparatively long storage periods of, for example, more than a year. A further important parameter for characterising the electrochemically activated saline solution obtained in this manner is the pH thereof, which essentially has a determining influence on the compatibility with other chemical substances or active ingredients, and also on the usability of the electrochemically activated electrochemically activated saline solutions in different environmental conditions and the like.

When producing electrochemically activated saline solutions of the above-mentioned type by electrolysis, it is thus generally sought, in the case of high storage stability, to ensure a particularly high bactericidal or antibacterial effect, characterised by a high content of free chlorine, the pH being intended to allow as good a compatibility as possible with other substances or active ingredients, or even being intended to remain adjustable, irrespective of the other parameters mentioned, as a type of free parameter.

As shown, achieving these design aims is dependent on a large number of parameters, for example when the method is performed, when the electrochemically activated solution is produced, when the plants used for this purpose are designed and also when the production process is designed in principle, for example with regard to media flow guidance. Within all these aspects and parameters, the design of the individual electrolysis cells, also referred to as a reactor, and in this context in particular also the structural configuration thereof, is also significant.

With respect to the design and the geometric construction of the individual electrolysis cells, also referred to as a “reactor”, a tubular or rod-shaped construction has proven successful in which the membrane is configured as a hollow ceramic body surrounded by an outer housing. In the case of a tubular construction of this type of the reactor or of the electrolysis cells, a first electrode is positioned in the interior of the hollow ceramic cylinder, whereas the other electrode is arranged in the annular chamber between the hollow ceramic cylinder and the outer housing, or is formed by the outer housing itself. In a construction of this type of the reactor or the electrolysis cells, the ion and electron migration and the ion exchange required for the electrolysis of the briny water solution takes place via the hollow ceramic cylinder provided as a membrane, out of the inner chamber thereof into the outer chamber surrounding it, or vice versa. The not previously published European patent application 10 014 854.3-1213 discloses an electrolysis cell for use in a plant for producing an electrochemically activated sodium chloride solution using said tubular construction of the type mentioned at the outset.

The problem addressed by the present invention is that of providing an electrolysis cell of the above-mentioned type, by means of which it is possible to produce an electrochemically activated sodium chloride solution which is of particularly high quality in terms of the above-mentioned design aims in a particularly advantageous and reliable manner, and which is particularly suitable for use in a plant designated for this purpose. Furthermore, a plant for producing an electrochemically activated sodium chloride solution, in particular using a quantity of electrolysis cells of this type, is provided, by means of which it is possible to produce sodium chloride solution which is of particularly high quality in terms of the above-mentioned design aims.

With respect to the electrolysis cells, this problem is solved according to the invention in that the ends of the hollow ceramic cylinder forming the membrane and the outer housing surrounding said cylinder are each mounted in a closure cap, which has a central hole forming an entry channel to the interior of the hollow ceramic cylinder forming the membrane and an annular chamber that extends around said central hole and, on the media side, is connected to the intermediate chamber between the membrane and the outer housing.

The invention proceeds from the knowledge that fulfilling the various above-mentioned design aims in order to provide an activated sodium chloride solution which is particularly high-quality in this case appears to depend to a considerable degree on highly exact and precise media flow guidance and material guidance. To make this possible, the electrolysis cell is to be designed so that the method can be performed in a reproducible and reliably controllable manner, which method particularly demonstrates reliably reproducible microscopic effects on ion migration and the corresponding conversion into the media flows with method parameters which are kept constant, such as flow rate, temperature, activation voltage applied and the like. To make this possible, the construction and structure of the electrolysis cell is to be designed for a particularly homogenous and uniform flow profile in anode and cathode chambers, in which the media flow can be kept largely free of disturbances, statistical interference and the like. In order to ensure this, particularly in the case of the tubular construction of the electrolysis chamber that is provided, an input and output for the flow medium are provided that are as uniform as possible, when viewed in the circumferential direction, for the outer region of the hollow ceramic cylinder, that is to say the annular chamber provided as an electrode chamber between the hollow ceramic cylinder and the outer housing surrounding said cylinder, in which turbulence caused by said input and output is to be kept particularly low.

This is achieved in that an annular collection chamber is assigned in each case to said annular chamber between the membrane and the outer housing at the inlet and preferably also at the outlet, into which collection chamber the medium is firstly fed and away from which collection chamber the medium can be carried again after passing through the annular chamber. In the collection chamber, homogenisation and thorough mixing of the medium fed in via assigned entry openings is provided, before said medium enters the annular chamber between the hollow membrane cylinder and the outer housing via a circumferential annular gap (it is the same on the exit side). Turbulence which could occur owing to the medium being input via entry openings and which could negatively affect the homogeneity of the flow when viewed in the circumferential direction is therefore directed away from the electrode chamber itself, formed by the annular chamber between the membrane and the outer housing, and into the upstream collection chamber. Environmental influences such as turbulence caused by the input can thus be kept away from the electrode chamber itself.

The medium or electrolyte thus enters and exits the annular chamber between the membrane and the outer housing via the circumferential annular gap and thus avoids transfer at points, as would be the case for example with connecting or transfer holes. In this case, the annular gap is particularly preferably dimensioned to be comparatively narrow, so that a comparatively high flow speed of the medium can be achieved when it flows through the annular gap caused by geometry. Owing to this local increase in the flow speed, additional homogenisation and harmonisation of the flow profile takes place.

Preferably, the outer housing surrounding the membrane is also designed as a hollow cylinder, particularly preferably made of metal. A design of the electrolysis cell which is tubular when viewed as a whole is produced, the hollow cylinder forming the outer housing being concentric with the hollow cylinder forming the membrane in a particularly advantageous configuration.

An additional metal body is arranged inside the hollow cylinder forming the membrane to form the electrode that is provided there. Said body is preferably designed as a metal central electrode that is also designed as a hollow cylinder, the interior of which electrode is connected, on the media side, via a quantity of transfer openings, to the annular chamber which is delimited by the inside of the membrane and surrounds said openings on the outside. For the inside of the hollow cylinder forming the membrane, it is thus possible to input the media flow to be treated, in the manner of a central arrangement, into the interior of said central electrode, the medium being transferred into the electrode chamber itself, that is to say the annular chamber between the central electrode on one side and the membrane on the other side, via the transfer openings.

In this case, the central electrode is preferably also concentric with the membrane. In combination with the outer housing, a construction of the entire system composed of the central electrode, membrane and outer housing is produced, which is concentric as a whole and is thus rotationally symmetrical, the electrode chambers themselves being formed on one side by the annular chamber between the central electrode and the membrane and on the other side by the annular chamber between the membrane and the outer housing. Owing to the symmetry, a particularly homogenous guidance of the media flow can be achieved on both sides of the membrane by this design of the electrode chambers as annular chambers which are positioned concentrically relative to one another.

In order to ensure particularly homogenous and disturbance-free guidance of the media flow into the electrode chambers themselves in the case of this design, the transfer openings provided in the central electrode are therefore preferably only arranged in the end region of the central electrode, that is to say in the immediate vicinity of the closure cap provided at each end. In a particularly advantageous configuration, all the transfer openings in the central electrode are, when viewed in the longitudinal direction of the arrangement, arranged in this case at most 10 mm, particularly preferably at most 5 mm, from the contact point of the hollow ceramic cylinder forming the membrane with the respective closure cap. In particular, the transfer openings are in this case advantageously positioned substantially within the plane formed by the end face of the closure cap. This construction in particular means that the “effective length” over which the media flows are exposed to electrolytic activation when flowing through the electrode chamber is the same both for the electrode chamber inside the hollow ceramic cylinder forming the membrane and in the electrode chamber arranged outside said hollow cylinder. A homogenous flow profile, in particular when viewed in the circumferential direction, in the electrode chambers on both sides of the membrane is thus ensured, both electrode chambers having a shared end plane with respect to the flow profile of the medium.

In a further advantageous configuration, the central electrode is provided at each of its ends with an inflow or outflow element which comprises a quantity of transfer openings and projects into the interior of said electrode, in a particularly preferred configuration the transfer openings in the inflow or outflow elements being in the same position as the transfer openings in the central electrode when viewed in the longitudinal direction of the membrane. Owing to this arrangement or positioning of the individual components relative to one another, the media can be conveyed into (or, on the outlet side, out of) the interior of the central electrode from outside via the inflow or outflow element and the transfer openings therein, it being possible for the medium to be further transported, when viewed in the same position in the longitudinal direction of the membrane, out of the inner region of the central electrode, via the transfer openings therein, into the annular chamber serving as an electrode chamber and surrounding the central electrode on the outside.

In combination with the annular gaps provided in each case for the media input and output into the outer annular electrode chamber, the transfer openings are in this case preferably selected and designed with respect to quantity, positioning and size such that a flow profile which is particularly uniform and homogenous overall is produced.

In a particularly advantageous configuration, which is also due separate inventive significance, the system is provided for swirl generation in the medium flowing through the respective annular electrode chambers. In other words, the system is advantageously designed such that the electrolyte primarily flows through the electrode chambers when viewed in the longitudinal direction of the membrane, a swirl in the media flow being superposed on said flow direction. Said swirl can be provided inside the membrane, outside the membrane or in both electrode chambers. As a result, the medium flowing through the electrode chambers is also caused by the arising centrifugal forces to be pressed against the respective outer walls of the electrode chamber, that is to say, for the inner annular chamber, against the inner wall of the membrane or, for the outer annular chamber, against the inner wall of the outer housing. Particularly close contact of the medium with the respective wall is thus produced, so that the transport processes relating to this are additionally promoted.

In the particularly preferred arrangement of the anode in the central region, the ion migration processes can be additionally promoted by a swirl generation of this type, by the Na⁺ ions produced being additionally pressed against the membrane, so that the imbalance produced between Na⁺ and Cl⁻ ions, caused by electrolysis, increases further. In the outer region, that is to say in the outer cathode chamber annularly surrounding the membrane, the swirl however causes the water to be brought into close contact with the cathode in an intensified manner, so that the H₂ formation and subsequently also the degasification is intensified. Both effects in combination particularly promote the production of NaOH.

The closure caps are provided on one hand, through the above-mentioned circumferential annular chamber, for homogenising, collecting and pre-distributing the flow media. On the other hand said closure caps are also provided, in a particularly preferred configuration, as support elements and also as insulating elements, via which the components, that is to say in particular the central electrode, membrane and/or outer housing, can be properly positioned relative to one another and, at the same time, said components can be reliably electrically insulated from one another. In addition, the closure caps are preferably made of insulating material, particularly preferably of plastics material, in particular of polypropylene (PP), polyethylene (PE) or in particular of polytetrafluoroethylene (PTFE).

In the manner of a conventional construction, the electrolysis cell could be configured such that the inner chamber of the membrane delimited by the central electrode is provided as an anode chamber and the annular chamber which is on the outside with respect to the membrane and is delimited by the outer housing is provided as a cathode chamber. Advantageously, however, the central electrode is designed as a cathode and the outer housing surrounding the membrane is designed as an anode. As a result of this, the annular chamber surrounding the membrane on the outside, that is to say the anode chamber, can in particular have a comparatively large cross-sectional area for the through-flow of the medium, so that a particularly disturbance-free media throughput can be achieved on the anode side.

In order to promote the electrochemical processes that take place during electrolysis, in particular regarding the desired ion migration and the conversion thereof into the electrochemical activation of the sodium chloride solution, the anode is, in an advantageous configuration, provided with a surface coating. In this case, the surface coating is, in terms of the selection of material, particularly preferably directed in a targeted manner towards the processes provided in the manner of a catalytic promotion of the reactions. Preferably, the surface coating therefore comprises the materials platinum and/or iridium and/or ruthenium and/or gold and/or diamond. In this case, in particular iridium and/or ruthenium may be present in a suitable form, for example as an oxide or a mixed oxide. Here, the coating component ruthenium oxide promotes, as a catalyst, a particularly high rate of production of oxygen-splitting substances, in particular measured in free chlorine, and can in this regard be provided in a suitable quantity as a component of the coating. In an alternative or additional advantageous configuration, the cathode is also provided with a surface coating which promotes the electrochemical processes, said coating particularly preferably being made of gold (Au). Advantageously, the layer thickness of the Au coating is approximately 1 μm.

In a further particularly preferred embodiment, which is also due separate inventive significance, the hollow ceramic cylinder forming the membrane is in a targeted manner, in terms of the selection of the material and the material properties thereof, adjusted to and directed towards the ion migration processes occurring during electrolysis. In addition, the hollow cylinder forming the membrane particularly preferably has a support body which is made of porous ceramic having an average pore size of at least 500 nm, preferably of approximately 3 μm. In a further advantageous configuration, a coating serving as a definition coating is provided on at least one of surfaces of said support body, said coating having an average pore size of at most 150 nm, preferably of approximately 100 nm. Advantageously, in this case α-Al₂O₃ having a pore size of approximately 3 μm is provided as the material for the support body and titanium dioxide (TiO₂) having a pore size of approximately 5 to 10 nm or α-Al₂O₃ having a pore size of approximately 100 nm is provided as the material for the definition layer.

Owing to this separately inventive combination, which relates to use in an electrolysis cell, of a comparatively large-pore support body with a comparatively small-pore definition layer, a fundamentally good material permeability of the hollow cylinder is provided, so that the ion migration processes beyond the membrane are particularly facilitated. In this case, the definition layer ensures that essentially the desired ions, chosen selectively in terms of their size, can migrate, while undesired secondary products or by-products can be filtered out. In a further advantageous configuration, the definition coating has an average pore size of at least 0.2 nm or 200 pm.

Advantageously, the definition layer is applied to the surface of the support body facing the anode side of the membrane, that is to say is applied to the inside in the case of the preferably provided construction having an anode chamber provided on the inside and a cathode chamber provided on the outside.

With respect to the plant for producing an electrochemically activated, water-based sodium chloride solution, the stated problem is solved by an electrolysis module, which comprises a plurality of electrolysis cells of the above-mentioned type, the anode chambers of the electrolysis cells being connected in series on the media side and the cathode chambers of the electrolysis cells being connected in parallel on the media side. By using the electrolysis cells of the above-mentioned type in a plant in which a targeted, sequential concentration of ions in the anolyte is ensured by this media flow guidance, a particularly high-quality, electrochemically activated solution can be produced in the context of the above-mentioned design aims.

In this case, particularly preferably, the anodes in the anode chambers are each provided with a surface coating, the material and composition of each surface coating being selected depending on the position of respective anode in the series connection of the anode chambers. As a result, in a particularly advantageous configuration, if necessary each anode can be provided with a catalytically active coating that is specifically directed towards the requirements within the series connection, so that, for example in a targeted manner, an increased rate of production of free radicals, split oxygen or the like can be set depending on the flow guidance within the series connection.

The advantages achieved by the invention consist in particular in that, owing to the inlet-side upstream arrangement and the outlet-side downstream arrangement, when viewed from the media side, of the annular collection chamber integrated into the closure caps, the media can, both on the inlet side and on the outlet side, enter or exit the annular electrode chamber surrounding the membrane on the outside in a particularly homogenous, turbulence-free and, when viewed in the circumferential direction, uniform manner. Therefore, possibly undesirably influential interference factors, such as the effects of turbulence, the formation of gas bubbles or the like, can thereby be prevented in the sensitive electrolysis processes, or said factors can be at least kept very low. In respect of the comparatively sensitive dependency of the material properties of the electrochemically activated solution produced on various process parameters, a reliable, reproducible and high-quality setting of the desired material properties is made possible thereby.

An embodiment of the invention is described in greater detail on the basis of the drawings, in which:

FIG. 1 shows a plant for producing an electrochemically activated saline solution by electrolysis;

FIG. 2 is a perspective view of an electrolysis cell for use in the plant according to FIG. 1;

FIG. 3 is a plan view of the electrolysis cell according to FIG. 2;

FIGS. 4, 5 are longitudinal sections of the electrolysis cell according to FIG. 2;

FIG. 6 is an enlarged detail from FIG. 4;

FIG. 7 is a perspective view of a closure cap of the electrolysis cell according to FIG. 2;

FIG. 8 is a longitudinal section of the closure cap according to FIG. 7; and

FIG. 9 is a cross section of the closure cap according to FIG. 7.

The same parts have been provided with the same reference numerals in all the figures.

The plant 1 according to FIG. 1 is provided for producing an electrochemically activated saline solution by electrolysis. For this purpose, the plant 1 comprises an electrolysis module 2, to which an electrolysis medium can be conveyed on the inlet side via a supply line 4. Softened or demineralised water to which brine or an aqueous saline solution has been added is provided as the electrolysis medium. For this purpose, the feed line 4 is connected on the inlet side to a water-softening station 6. To add the brine to the softened water, a Venturi nozzle 8 is connected into the feed line 4 and is in turn connected on the inlet side to a brine container 10. An outlet line 12 also branches off from the feed line 4 downstream of the water-softening station 6, via which outlet line, during a start-up phase of the plant 1, the flow of water can be discharged from the water-softening station 6, bypassing the electrolysis module 2 of the subsequent components, into the brine container 10. In order to switch between said operating states including the continuous operation state and to input a predetermined amount of brine in a dosed manner into the electrolysis medium, suitable valves 16, 18, 20 are connected into the feed line 4, the outlet line 12 and the brine input line 14 which discharges into the Venturi nozzle 8, and a throttle valve 20 is connected into the input line 14.

On the outlet side, for discharging the electrochemically activated saline solution produced in the electrolysis module 2, an outflow line 24 is connected to the electrolysis module 2 which discharges on the outlet side into a supply container 26 for the produced saline solution or the anolyte. In order to temporarily bypass the supply container 26 during the start-up phase of the plant 1, a multi-way valve 28 is also connected into the outlet line 24, the second outlet of which valve is connected to a drain line 30.

The plant 1 is designed to produce an electrochemically activated saline solution having particularly advantageous properties for use as a disinfectant or an antibacterial active substance in medical and therapeutic applications, for example, in particular having a particularly high content of free chlorine of preferably greater than 500 mg/l and in particular approximately 800 mg/l, but optionally even greater than 2000 mg/l in the case of a long storage life. To make this possible, the electrolysis module 2 has a multicomponent construction and comprises a plurality of electrolysis cells 40, 41, of which only two are shown in the embodiment; as in the following embodiments, additional electrolysis cells 40, 41 can of course also be provided.

Each electrolysis cell 40, 41 comprises a cathode chamber 42 forming a first electrode chamber and an anode chamber 44 forming a second electrode chamber, which chambers are separated from each other by a membrane 46. Applying a voltage between an anode delimiting the respective anode chamber 44 on one side and a cathode delimiting the respective cathode chamber 42 on the other side thus causes ion migration across the interposed membrane 46, so that an at least partial dissociation of the water contained in the electrolysis medium and an at least partial dissociation of the salt proportions, entrained in the form of brine, and the electrolysis derivatives thereof occurs. Owing to the electrical charge of the ions in these materials, this ion migration process owing to the applied voltage leads to an accumulation of Cl⁻ and OH⁻ in the respective anode chamber 44 and to an accumulation of H⁺ and Na⁺ in the respective cathode chamber 42. In order if necessary to conduct away hydrogen gas that has accumulated as a result in the respective cathode chamber 42 or the first electrode chamber, each cathode chamber 42 is connected to a degasification line 47. Said line forms, optionally in combination with means arranged in the cathode chamber 42 for bubble generation or gas deposition, such as swirlers or the like, a degasification module for the respective cathode chamber 42.

The desired high-quality properties of the electrochemically activated saline solution are achieved in the plant 1 in particular by a specific guidance of the media flows in the electrolysis module 2. In this case, in the plant 1, media flow guidance which is substantially parallel on the cathode side is combined with media flow guidance which is substantially in series on the anode side according to the embodiment which is directed in a targeted manner towards providing electrochemically highly activated anolyte. Alternatively, or if there is a different design aim, media flow guidance which is substantially parallel on the anode side can also be combined with media flow guidance which is substantially in series on the cathode side. In addition, yet further combinations of these media-side connections can be provided.

Specifically, in this case, a branching point 48 is provided in the feed line 4 in the plant 1 in the embodiment, from which point feed-in lines 50 discharging into the cathode chambers 42 of the electrolysis cells 40, 41 exit in the manner of parallel media guidance. On the outlet side of the cathode chambers 42, outflow lines 52 are provided which are brought together to a convergence point 54 so that overall, the cathode chambers 42 are connected in parallel on the media side.

On the anode side, however, the anode chambers 44 for the anolyte are connected in series or in parallel. For this purpose, the anode chamber 44 assigned to the first electrolysis module 40 when viewed in the flow direction of the anolyte is connected on the outlet side via an transfer line 56 to the inlet side of the subsequent anode chamber 44 arranged in the second electrolysis module 41. Said chamber is in turn connected to the outflow line 24 on the outlet side, so that the anode chambers 44 or the anolyte are connected in parallel in a multi-stage or cascade-like configuration.

In addition, it is provided in the plant 1 that the catholyte flowing out of the cathode chambers 42 is fed as anolyte into the anode chambers 44 which are connected in parallel. For this purpose, the convergence point 54 for the catholyte is connected via an transfer line 58 to the anode chamber 44 of the electrolysis cell 40 which is first when viewed in the flow direction of the anolyte.

A discharge line 60 also branches off from the transfer line 58 in the convergence point 54, via which discharge line a partial flow of the catholyte, the quantity of which partial flow can be adjusted via throttle valve 62, can be conveyed to a waste water system or to a collection container 64. By means of this arrangement, it is possible to convey an adjustable partial quantity of the catholyte flowing out of the cathode chambers 42 as anolyte to the cascade of anode chambers 44. The individual reaction parameters, such as pressure and flow speed in the anode chambers 44, inter alia, can be suitably influenced thereby, and in addition the quantity of the catholyte accumulating in this application as a “waste product” can be kept particularly low.

To check the material properties of the anolyte produced and to measure quantities, a number of sensors, in particular a quantity sensor 66, a temperature sensor 68, a pH sensor 70 and a sensor 72 for measuring the redox potential, are moreover connected into the outflow line 24.

In terms of structure, the electrolysis cells 40, 41, as shown in a perspective view in FIG. 2, a plan view in FIG. 3 and in a longitudinal section in FIGS. 4 and 5, are constructed so as to have a substantially cylindrical basic shape and thus a tubular or rod-shaped construction. In this case, a hollow ceramic cylinder 80 is provided as a membrane 46 and is surrounded on the outside by an outer housing 84 which is also designed as a hollow cylinder 82. In this case, the outer housing 84 is additionally provided as an electrode for the electrolysis cell 49, 41 and is accordingly made of metal, in the embodiment is made of titanium. The ends of the hollow ceramic cylinder 80 forming the membrane 46 and the outer housing 84 surrounding said hollow ceramic cylinder are each mounted in a closure cap 86, which in turn is mounted on metal end plates 88 on end plates 90 on the ends of the outer housing 84. As can be seen in particular from the plan view in FIG. 3, the media connections 92 of the electrolysis cell 40, 41 are only provided in the region of the closure caps 86.

From the view of the electrolysis cell 40, 41 in longitudinal section according to FIGS. 4 and 5, it is clear that the hollow metal cylinder 82 forming the outer housing 84 is concentric with the hollow ceramic cylinder 80 forming the membrane 46. In addition, a metal central electrode 96 which is in turn also designed as a hollow cylinder 94 and is also concentric with the hollow ceramic cylinder 80 forming the membrane 46, is arranged within the membrane 46 and is used as a second electrode of the electrolysis cell 40, 41 in addition to the outer housing 84.

In this tubular or rod-shaped configuration of the electrolysis cell 40, 41, the electrode chambers through which the electrolyte flows are thus formed, on one side, by the first annular chamber 98 formed by the intermediate chamber between the central electrode 96 and the membrane 46 and, on the other side, by the second annular chamber 100 formed by the intermediate chamber between the membrane 46 and the outer housing 84. With respect to the electrical circuit, the electrolysis cell 40, 41 can in this case be constructed in the manner of a “conventional” configuration, such that the inner, first annular chamber 98 is provided as an anode chamber 44 and the outer, second annular chamber 100 is provided as a cathode chamber 42. In the embodiment, however, the inner, first annular chamber 98 is designed as a cathode chamber 42 and the outer, second annular chamber 100 is designed as an anode chamber 44, for particularly extensive homogenisation of the flow profile of the electrolyte and advantageous media flow guidance, in particular in terms of the throughputs which can be achieved.

Accordingly, the central electrode 96 is used as a cathode, whereas the outer housing 84 is provided as an anode. Accordingly, the material selection is also provided for said components. The central electrode 96 provided as a cathode is, in this case, constructed as a metal base body, in particular made of titanium, and is preferably provided with a surface coating which particularly promotes the function thereof, and in the embodiment this is a coating of gold (Au) having a thickness of approximately 1 μm. The outer housing 84 provided as an anode is also formed by a base body made of titanium which, on the inner surface of the hollow cylinder thereof facing the anode chamber 44 or the second annular chamber 100, has a suitably selected surface coating 102, in particular comprising iridium (Ir), ruthenium (Ru), gold (Au) and/or diamond.

The electrolysis cell 40, 41 is particularly designed for producing particularly high-quality electrochemically activated sodium chloride solution, a particularly high content of free chlorine and/or a high redox potential being sought in particular, together with a storage stability that is particularly high overall. To make this possible, the structure of the electrolysis cell 40, 41 is designed for particularly uniform and homogenous media flow guidance when the electrolyte flows through the electrode chambers, it being intended in particular for interference effects owing to turbulence, gas bubble formation and the like to be kept particularly low.

The closure cap 86 which is arranged on each end of the base bodies of the above-mentioned components and is shown in a perspective view in FIG. 7, in a longitudinal section in FIG. 8 and a cross section in FIG. 9 is suitably constructed for this purpose. In particular, the concept forming the basis for the configuration of the closure cap 86 is that the effects of turbulence occurring when the electrolyte is input into and output from the electrode chambers should be therefore shifted out of the electrode chambers themselves. For this purpose, the closure cap 86 has a central hole 110, via which the electrolyte can be input into the interior of the hollow cylinder 94 forming the central electrode 96. However, in order for it to be possible to supply the second annular chamber 100 provided as an anode chamber 44 and surrounding the membrane 46 on the outside with medium in a particularly homogenous and turbulence-free manner, the closure cap 86 has an annular chamber 112 surrounding the central hole 110 forming the entry channel to the interior of the central electrode 96, which annular chamber can function as a collection chamber or distribution chamber. The respective media connection 92 discharges into the annular chamber 112.

As can be seen particularly clearly from the longitudinal section according to FIG. 8 and the cross section in FIG. 9, the closure cap 86 also comprises a first annular groove 114 provided for receiving the hollow cylinder 80 forming the membrane 46 and a second annular groove 116 provided for receiving a sealing ring. In the region between the annular chamber 112 and the first annular groove 114, the closure cap 86 comprises a sloping edge 118. Said edge corresponds with an associated edge 120 in the flange region of the outer housing 84. The closure cap 86 and the outer housing 84 are in this case dimensioned and constructed such that when assembled, the edges 118, 120 form a circumferential annular gap, via which the annular chamber 112 is connected on the media side to the second annular chamber 100, forming the anode chamber 44, between the membrane 46 and the outer housing 86.

Owing to this structural configuration, a rotationally symmetrical and thus particularly homogenised media-side connection of the annular chamber 112 in the closure cap 86 to the annular chamber 100 forming the anode chamber 44 is produced within the outer housing 84. The annular chamber 112 in the closure cap 86 is thus used as a collection and distribution chamber, the media being input from outside firstly into the annular chamber 112 via the media connections 92. From there, the input medium is homogenised, and all turbulence takes place in the annular chamber 112. From there, the medium can then be homogenised and can flow into the anode chamber 44 via the annular gap formed by the edges 118, 120, without any further disturbances.

In one variant, the electrolysis cell 40, 41 is provided for swirl generation in the medium flowing through the annular anode chamber 44 and optionally also in the medium flowing through the cathode chamber 42. As a result, the medium flowing through the electrode chambers is also caused by the arising centrifugal forces to be pressed against the outer wall of the respective electrode chamber, that is to say, for the cathode chamber 42, against the inner wall of the membrane 42 and, for the anode chamber 44, against the inner wall of the outer housing 84. Particularly close contact of the medium with the respective wall is thus produced, so that the transport processes relating to this are additionally promoted. In order to produce the swirl when inputting the medium into the outer annular chamber 100 provided as an anode chamber 44, in this case the circumferential annular gap formed by the edges 118, 120 when assembled can be suitably constructed, in particular contoured, and/or suitable means for swirl generation, such as guide fins, baffle plates or the like can be provided in the inflow region of the medium, that is to say in particular in the region of the annular gap.

Optionally, yet further suitable means for swirl generation can also be provided in the medium flowing through the electrode chambers, for example inner ribbing of the respective hollow cylinder 80, 82, 94 constructed as a “drawn tube” or rippling on the inner surface.

The closure caps 86 are provided on one hand, through the above-mentioned circumferential annular chamber 112, for homogenising, collecting and pre-distributing the flow media. On the other hand said closure caps 86 are however also provided as support elements and in addition as insulating elements, via which the components, that is to say in particular the central electrode 96, the membrane 46 and the outer housing 84, can be properly positioned relative to one another to form an overall concentric arrangement, and at the same time said components can be reliably electrically insulated from one another. For this purpose, the closure caps 86 are made of plastics material, specifically of PTFE in the embodiment, so that the desired insulating effect is ensured.

The inner chamber of the central electrode 96 is fed with medium via the central hole 110. So that the electrolyte in this inner region of the hollow cylinder 94 forming the central electrode 96 can enter the first annular chamber 98 forming the cathode chamber 42 and surrounding said hollow cylinder, the end regions of the central electrode 96 are provided with a quantity of transfer openings 130. Said openings produce a media-side connection of the inner chamber of the hollow cylinder 94 to the outer chamber thereof, that is to say to the first annular chamber 98. The transfer openings 130 are in this case positioned, when viewed in the longitudinal direction of the electrolysis cell 40, 41, such that as far as possible, an identical “effective length” for the cathode chamber 42 on one hand and the anode chamber 44 on the other is produced. For this purpose, the transfer openings 130 are arranged only in the end region of the hollow cylinder 94 forming the central electrode 96, such that they are substantially in the plane defined by the end plate 90 of the outer housing 84. In particular, the transfer openings 130 are in this case positioned such that they are offset at most by 5 mm from the end face of the respective end plate 90.

For the controlled input of the medium into the inner chamber of the central electrode 96, an inflow and outflow element 132 is arranged in each central hole 110, which element projects into the respective central hole 110 in the manner of a guide sleeve and is provided at its ends with transfer openings 134 for the electrolyte. In order to ensure a particularly homogenous input and output of the media here, the transfer openings 134 are arranged, when viewed in the longitudinal direction of the electrolysis cell 40, 41, in substantially the same position as the transfer openings 130 in the central electrode 96. The main through-flow direction of the transfer openings 134 can be substantially radially oriented. In the embodiment, the system is however provided for swirl generation in the medium flowing into the inner chamber of the central electrode 96. As a result, the medium flowing through the inner chamber of the central electrode 96 is also caused by the arising centrifugal forces to be pressed against the inner wall of the central electrode 96. For this purpose, the main through-flow direction of the transfer openings 134 is oriented so as to be inclined, and said openings thus also have a tangential directional component in addition to a radial directional component.

As can be seen in particular from the enlarged detail shown in FIG. 6, the hollow ceramic cylinder 80 forming the membrane 46 is also, in terms of the selection of the material and the material properties thereof, particularly directed towards the electrolysis processes which are occurring. The hollow ceramic cylinder 80 forming the membrane 46 is suitably constructed for this purpose and in particular has a support body 140 which is made of porous ceramic (in the embodiment α-Al₂O₃) having an average pore size of at least 100 nm (in the embodiment approximately 3 μm). Owing to this selection of the porosity, in particular an overall comparatively easier ion transport is made possible which has suitably higher ion permeability and sufficiently high mechanical stability of the support body 140 for use over a long period of time. In this case, however, in order to promote the ion migration processes that are desired for the particular use and to minimise side effects and disturbance processes, the inner surface of the support body 140 comprises a coating 142 serving as a definition layer and having an open porosity of approximately 40 to 55%. The coating has comparatively small pores in comparison with the comparatively large-pore support body 140, and has an average pore size of between 0.2 nm (200 pm) and 150 nm (in the embodiment approximately 100 nm). The coating 142 serving as a definition layer could in this case be made for example of titanium dioxide (TiO₂) having a pore size of approximately 5 to 10 nm. In the embodiment, α-Al₂O₃ having a pore size of approximately 100 nm is provided as the material for said layer.

LIST OF REFERENCE NUMERALS

-   1 plant -   2 electrolysis module -   4 supply line/feed line -   6 water-softening station -   8 Venturi nozzle -   10 brine container -   12 outlet line -   24 outflow line -   26 supply container -   28 multi-way valve -   30 drain line -   40, 41 electrolysis cell -   42 cathode chamber -   44 anode chamber -   46 membrane -   47 degasification line -   50 feed-in line -   52 outflow line -   54 convergence point -   58 transfer line -   60 discharge line -   62 throttle valve -   64 collection container -   66 quantity sensor -   68 temperature sensor -   70 pH sensor -   72 sensor -   80 hollow ceramic cylinder -   82 hollow cylinder -   84 outer housing -   86 closure cap -   90 end plate -   92 media connection -   94 hollow cylinder -   96 central electrode -   98 first annular chamber -   100 second annular chamber -   102 surface coating -   110 central hole -   112 annular chamber -   114 annular groove -   116 annular groove -   118, 120 edges -   130 transfer openings -   132 inflow/outflow element -   134 transfer opening -   140 support body -   142 coating 

What is claimed is: 1-15. (canceled)
 16. An electrolysis cell, comprising: an anode chamber having an anode; a cathode chamber having a cathode; a membrane separating the anode chamber from the cathode chamber, said membrane configured in the form of a hollow ceramic cylinder; an outer housing in surrounding relationship to the hollow ceramic cylinder; and a closure cap configured to support an end of the hollow ceramic cylinder and an end of the outer housing, said closure cap having a central hole which forms an entry channel to an interior of the hollow ceramic cylinder, and an annular chamber which is sized to extend around the central hole and connected on a media side to an intermediate chamber between the membrane and the outer housing.
 17. The electrolysis cell of claim 16, constructed for producing an electrochemically activated sodium chloride solution.
 18. The electrolysis cell of claim 16, wherein the outer housing is constructed as a hollow cylinder.
 19. The electrolysis cell of claim 16, wherein the outer housing is made of metal.
 20. The electrolysis cell of claim 16, wherein the outer housing is disposed in concentric relationship to the membrane.
 21. The electrolysis cell of claim 16, further comprising a metal central electrode constructed in the form of a hollow cylinder and arranged inside the hollow ceramic cylinder, said central electrode having an interior which is connected, on the media side, via a plurality of first transfer openings to an annular chamber which is delimited by an inside of the membrane and surrounds the transfer openings on the outside.
 22. The electrolysis cell of claim 21, wherein the central electrode is disposed in concentric relationship to the membrane.
 23. The electrolysis cell of claim 21, wherein the transfer openings are only positioned in end regions of the central electrode.
 24. The electrolysis cell of claim 21, wherein the central electrode has ends, each end being provided with an inflow/outflow element which comprises a plurality of second transfer openings and projects into the interior of the electrode, said second transfer openings of the inflow/outflow element being arranged in a same position as the first transfer openings of the central electrode, when viewed in a longitudinal direction of the membrane.
 25. The electrolysis cell of claim 24, wherein the second transfer openings are inclined when viewed in a radial direction.
 26. The electrolysis cell of claim 16, wherein the closure cap is made of insulating material.
 27. The electrolysis cell of claim 26, wherein the insulating material is a plastics material.
 28. The electrolysis cell of claim 27, wherein the plastics material is selected from the group consisting of PP, PE, and PTFE.
 29. The electrolysis cell of claim 21, wherein the central electrode forms a cathode and the outer housing forms an anode.
 30. The electrolysis cell of claim 29, wherein the outer housing as anode has a surface coating.
 31. The electrolysis cell of claim 30, wherein the surface coating comprises platinum, iridium, ruthenium, gold and/or diamond.
 32. The electrolysis cell of claim 29, wherein the central electrode as cathode has a surface coating.
 33. The electrolysis cell of claim 32, wherein the surface coating comprises gold.
 34. The electrolysis cell of claim 32, wherein the surface coating has a layer thickness of approximately 1 μm.
 35. The electrolysis cell of claim 16, wherein the hollow cylinder has a support body made of porous ceramic having an average pore size of at least 100 nm and provided on at least one of its surfaces with a porous definition coating having an average pore size of at most 10 nm.
 36. The electrolysis cell of claim 35, wherein the definition coating has an average pore size of at least 0.2 nm.
 37. A plant for producing an electrochemically activated, water-based sodium chloride solution, comprising: an electrolysis module including a plurality of electrolysis cells, each of the electrolysis cells comprising an anode chamber having an anode, a cathode chamber having a cathode, a membrane separating the anode chamber from the cathode chamber, said membrane configured in the form of a hollow ceramic cylinder, an outer housing in surrounding relationship to the hollow ceramic cylinder, and a closure cap configured to support an end of the hollow ceramic cylinder and an end of the outer housing, said closure cap having a central hole which forms an entry channel to an interior of the hollow ceramic cylinder, and an annular chamber which is sized to extend around the central hole and connected on a media side to an intermediate chamber between the membrane and the outer housing, wherein the anode chambers of the electrolysis cells are connected in series on the media side, and wherein the cathode chambers of the electrolysis cells are connected in parallel on the media side.
 38. The plant of claim 37, wherein the anodes of the electrolysis cells are each provided with a surface coating of a material and composition which are selected depending on a position of each anode in the series connection of the anode chambers. 